Friction gear



vs'epge 1930.v y J RTE'R 1,775,479

FRICTION GEAR Sept. 9, 1930. v l J, ARTER 1,775,479

FRICTION GEAR Filed July 17, 1929 2 Sheets-Sheet 2 SMSQQM y Patented Sept.` 9i, .1930

UNITED STATES PATENTEOFFICEtfijf JAKoBfAaTER, or onen-ENGSTRINGEN, sWnrzEnLANn rammen enana` y i `iippiicationyfiled'July 17,"192'9,`seiia1 No. 378,989, anein switzerland July 21g-1328,]

q `Thepresent invention has relierenceto fric tion Igears "and particularly to a device i'or generating the required pressure between the engaging" surface-s ofthe drivingand driven friction members ofsuch gears. It isrlrnovvn in frictiongears to utilize theimomentum to be transmitted l for "generatingil the required pressures" betweenthe engagingfq `friction surfaces.` and to this end ,sucht gearsjcomprise preferably a pairof cam disksandballs engaging "between these' disks and "displacing the latter more for less" according 'to the momentum "transmitted through the balls. When `thesefdisks are angularly `displaced 'relatively'to each other through the transmitted momentum the balls roll, on ,the inclined t tracksfandgenerate `with the latter'anl axial u thrust anddpressure action of Whichthe latterisin direct proportontojthe momentum to l rtypeseriA tleirpurpose onlyzi-eitherno axialltraveljorfenly"a short one isreqiiired u andif the anggglesbi` inclination of the aXially `too Vsmall .as othervvise `a comparatively lshort axialY movement requires such"` aglarge angu- `chilled Ain one ivorkingf step so lthat inaccuh V racies and thereby unequal contactbetween thevarious'lballsand cam-tracks'occurs. y j LILhOWever, `large axial displacements are necessary, VWhich is particularly thecase with c gearsgin vvhichthe ratio `of speed is' altered b yl aiiial displacement. offfrictinrmenibers or of y devicesrail;` if y Iir` rder to provide aldevice vfor Ye'rierating.

` the necessarycbntact `pressure also inthe last Y mentioned casesvvithlfriction gears inwhich acementof atl leastfonerolling track;f

` 9 sary axialfmovementfand'theaxialjpressure required tofp vent afgliding'yo i lip'be-` `tween theengr tact pressure in `friction gears permits "adu sufficient space to arrange thenuniber of `balls extending` cams of therdisks are notch`osenV 2'5 'in Which the grooves of the screw thread `constructional example of thejtype` Which al-"f` -he`rolling`tracks respectively, the known, u u

lowsl ageneraftionf of the contact pressure 4for i i the me@ of speed isaneredeaugeeibyan ma according tothe preseiitfinvention the neces-qy y Y q bingsurfaces"rellingonleach. u im otheris casedQinstea'dl-o'f bylapluralityof thread) `Which areguidedlbyr a cage follow- '65 ing; theV movementgof the thread.` Such ball i threadsfarelinovvn `per se, "however their appheationas means Vfor generating the convantages not obtainable with other devices.` The threads Ymay be produced in a` single Working step and do not require a special justing device. Further suchthreads may be produced lof any length'sothattliere 65 required in View of the strength; moreover longerftravel Jfor adjustmentpurposes isyobd tained leven itsmalleranglesbf inclination i havetobeused. i

y Several embodiments ofithein'ventibn `are :7U i `illustrated by ivayfof exampleon the iaccenrV panying drawings, in which f Figilshovvspartly in-elevationkand inan a-Xialsection a con'structional `example serving for" transmitting the npower "aremjnt` i one'half directly intoV a shaftof the lgear andy theotherhalf into "member c'onneclted vvitlr w vonelrollingffacingi" f f Fig; 2 shows in anaxial section aco'nstruceen in which the bau uli-@aa Shows @a left;

hand and right-hand part, vvhilstf "Figs-13,4; and Ll@"slrowgin fan axial section 1 tvvo" constructional "examples in which'A 'the j grooves l of theball thread rare into two 4 bushes arranged eoncentrically onein'side the" V ,otherf u i `F1g. 5' shows 1n1 an axialsection a further both directions of rotation ofthe gear,4k and Gfshows onfa larger scale an axiallsec# tion` throupfhapartjoif` the ball threadandof acageserving` to guide theballsl Figifshovvs partly in elevat on an thread; "vvhich together with `an annular guide Y eo i i, in an "axial: section aportion of gear u 'y q t `which] `is `prov1ded,' besides a mainthreajdj v Y i. "serving for power transmission, lan auxiliar H the cage guiding the balls from the intended position. Y

Fig. 8 is a diagrammatic view serving to explain the operation of the device illustrated in Fig. 7, and

Fig. 9 shows partly in elevation and partly in an axial section a portion of a gear in which the deviation of the cage guiding the balls from the intended position is prevented by a torsional spring provided with an initial tension.

Referring now to the drawings in all the constructional examples 1 denotes the driving shaft and 110 the driven shaft of the friction gear, which is completely shown only in Fig.

Vl, and 2 designates a member provided witl a rolling track orV race 21V of that gear.

In the construetional example illustrated in Fig. l the grooves of the thread are cut one half directly in the shaft l and the other half in the menjiber2. 'lhe two parts l and 2 concentrically arranged one in the other have only indented screw thread grooves 22 and 23V respectively (see also Fig. 6), and no radially interengaging combs or ribs. into the helical grooves balls 2li are inserted whereby any axial thrust is solely taken up by the latter. Asi long as the balls are not inserted int-o the helical grooves4 22 and 23 respectively the two parts lV and.2 may be freely displaced. in the axial direction .relatively to each other. The balls 24s are held and guided by a tubular cage 25. The two rings 2G, 2T inserted at the ends of the member 2 serve to guide the latter on the shaft 1 and toact as abntments for the ball cage 25. The length of the latter must be shorter than the distance between the two abutment rings 2 6, 27 by at least the length of travel for the adjust-ment. Y

l/Vhen power is transmitted by the above describedV device the transmitted moment screws the part 2 on the shaft l towards the left and presses it againstvthe rolling inein-V bers 3, which roll on a rollingptrack or vrace 21, provided on the left hand end Vof the part 2, and on the rolling track 2l of a stationary part 210 and on a track 211 rigidly fixed to the driven shaft 11". By suitably choosing the anglevof inclinati-on of the ballthread 22, 23, 24; the contact `pressure between the members 3`and the rolling tracks 21, 2l and 2li may beybrought into the required ratio to the power to be transmitted. The device illustrated in Fig. l in only be Yused for one direction of rotation the friction gear, as in the opposite direction of rotation the member 2 provided with the rolling track 2l isscrewed towards the and is vthus moved ont of contact \.ith tne rolling ineminstead of being pressed against the bers o latter. Y

The constructional example illust-rated in 2i-permits the required contact pressure be weon theengaging .surfaces of the driving and driven friction members, for both directions of rotations of the gear. ln this constructional example the ball thread is provided with a right hand threaded part 28 and a left hand threaded part 29 each of which is arranged in separate sleeves 30 and 3l respectively` The thread grooves are cut one half directly in the shaft l and the other half in the sleeves 30 and 3l respectively. Each of the sleeves 30, 3l is connected to the member 2 by means ofl grooves and keys 32 and 33 respectively so that it is axially displaceable but not turnable on said member. For each sleeve an abutment 30l and 311 respectively is provided on the member 2; these abntments act asa stop for the sleeves in the `direction in which they have to exert `an axial pressure on the friction members, while in the other` axial .direction the .movement` of said sleeves is not restricted as the inner ends of the two sleeves 30, 31 are separated from each. other by a comparatively large intermediary space 34, In this manner in every direction of rotation ofthe shaft l one of the two sleeves 3l, 32 urges the member 2 towards the left while the vother is relieved. Thus in one direction. of rotation of the shaft l only one of the two threadedparts 28, 29 is operative, the other part being operative when the shaft l rotatesin the opposite v.di-

rection. e. y .i y

In the const-ructional example illustrated in Fig. the grooves 22, 23 of the ball thread are cnt in sleeves 34 arranged concentrically one within the other,` The inner sleeve is` connected withthe shaftl ofthe gear` b v means of` axial grooves 36 andballs 37. and the outer sleeve 35` with the member 2 carry-V ingone of the rolling tracks not shown` by meansofaXial.grooves 3,8'and balls39.; both connections are such as to permitV axial displacement ofthe sleevesi and prevent an angular displacement. The fmoinentumv to be transmitted by the sha.. ,'lftends to nnscrew the two sleeves: 3411,35, whereby, depending on the; direction ofV rotation of the` shaft l, in the one case the inner sleeve 34 is screwed towards theleft .and the outer sleeve 35towards .the right andhin the other case the outersleeve. 35 is ,screwed` towardsthegleft and-the inner sleeve3et`ytowards the right. 'lhe Yac tion is, however" the same in both cases, inasmuch as {alwi one of the sleeves 34, 35 urges the member 2 Yby theintermediary of a ball'thrust bearing 40 towards the-left while the other sleeve bears towards the righton the shaft l by the intermediary of a ball thrust bearing Lll anda ring 42.?, The two ball thrust bearings 40, lllare onlyA required forvone'direction of rotation, ,that is to say for that .direction in which eachsleeve exertsits axial pressureonthe part which is not connected to it but Vwit-lrvvrhich it is in a ro'- y thevr'in'gsf47f481thisainplifying ratio may` constructional example with one'direction of iotationfof the shaft 11g for instance; the inf c `ne'rsleeve` 43 is displaced'towards the left, "ld i.e; towards-the memberZcarrying alrolling trackft-hey supporting ball's 49 are wedged in oi?` rotation of 1-the shaft l" and permits con-` siderablyi'large displacements for adjusting purposes.: 1 c c ci i. Y c .i

'Figf 4sshows also ay constructional example l in which twosleeves43,144" provided with helical grooves and arranged concentrically one within the ether are used. Thethreaded sleeves 43,44 are axially'. displaceable but not turnably connected @to their appertaining parts l and-2 by 'means `ofkeys '45 and 46` respectively; Ealcli' sleeve` 43;' 44 rests l with l 4The rings47,48` abutfagainst a row of'balls "between the member 2` aiid-tlieconical `ifacing on the` thrusty ring'f 48 of theuouter sleeve 44,

c fiirhe'reby tli'ermeniber' V2 is 'urgedvtowards the leftwvith allarger force" than inthe casein.

whic'hft-he hall thread 50fwould act directly f on the fmemberQ. In the opposite direction 'f'liotation' the two screw threadedsleeves 43.44 exchangegtheir roles@` By choosing `the angle ofinelination of th'econical facings of `straight inclined facings'on the rin`gsf`48,

4723s lis shown in" Fig. 45,' to maintain con etant thefratiobetween` theV force exerting the contactpressure and the power to be trans- `.initted along the total displacement path, or

bygchoosing curved inclined facings on the rngstu 48 aS 1S shown in Fig." 4, tovary f r c the ratio between said force'cand power,

"5 `shows a further constructional exampleadapted for both directions of rotation,` in which one-haltl ofthe `thread is cut 4 to themember2,'while Ainthe case of an anti-clockwise rotation*of-the4 shaft I and a' displacement `oi? the threaded sleeve 4towards the right a ring 5 is pressedwith its `conical thrust facing against thrust balls 6 arranged around the shaftL` Thereby these `balls `6 are pressed inthe manner of awedge foto `between a ring 7 thescon'ical right hand. end of the member 2 whereby the axial pres- Y sure isredirected into the direction in which y the Contact pressure hasl tobe exerted.

i i .Vith frictionlgears providedwitli devices "of the described type for" generating there? quired 'pressure betweenv the engaging surfaces ofthe Jfriction members it mayoccur when the balls are relieved of the load,1 for instance when the gear runs idle,` that the cage guiding the balls rotates with the latter in `an undesired manner independently of the parts in which the threadis cut and finally abuts against one of the two abutments serving to i limit `the axial displacement of the cage. i In this case the anti-friction' action of theballs` ceases andthe exertion oftlie'contact pres- `sure required for the transmissionof power Y In order to iobviate this *disadvantage i means may" be'provided,` in `the mannerillus" tratedin Figs. 7 andx9,"to `prevent any devia#V tionof the cage `2`5fforguiding the balls 24` from theposition which `tlie1balls24 assume.- i y when rollinginfa slipless"manner:V c In Fig. 7 the referencelgl Adenotes again a shaftfofthetriction gear,2 is a sleeve providedwith arolling track 2L and 3 designates and L 23" denoteV the helical` grooves of the; thread serving 4to transmit the' power; 24 are the-balls inserted in the grooves *an`d`25c de'sigr` nates A` also in l` this embodiment the cagel for Vguiding the balls 24a 'Ilie shaftll isifurther piovidedwitli an auxiliary threadSO" which f hasl aninclination that i is `differegnt "from the" 'nclinationgI of `theffrnain` i thread formed by i y the grooves 22;* 23'. "IIifthe` auxiliary 'thread 8O lafball `8`5"`is inserteldffIn theisleeve 2 la Y l i n ring 84liaving an annulargroove 87 *and sur-y` rounding the shaft 1 is'provided and theball 84 is inserted inthe sleeve 2 with axial' cleara rollingmember which is `only partly'shown i and cooperates withfthe rolling tralclr21.`V` 2 2 ance andin the latter springs 89 and QQ are inserted at both sides of the ring 184 to li'old the latter `in `a middle position. The axial clearance 'of ther ring `84 in the 'sleeve 2 is intended to equalize any inaccuracy inathe c'ooperationloi thetwo threads 80. and 22,1 231' l i due toinaccuraciesinthe manufacture offthe' balls 85, 24` or their inaccurate 'rolling'.` The its Smiddle positiorijeve'ry timeithe main sloti 86 provided Ain" the cage 125lwhereby` the;

`latter is r'eevto move in the axial idirectlio'nl:1

y relatively to `the hal-185 but not "inthe direc,y ytion of rotation. AArs the two pathsof the c ball S5, annular groove Saiid tln'eadgroove 8O have not the `same direction the ballS 'can @my belintue' 'point pffinters'eaionof that@ i center linesl of these twoypaths'which isfar definite point orevery position` ofthe sleeve t `.2 onthe sliaftTl; Asf'the movement of `the cage 25 aroundtlie shaftfl is dependent on" the "positionof the ball 85 and the axial lad# illstlflntf the @eee 125 isldieimiriea ifi ne lmequvbal manner "by the main thread; 22;

es Winni-,helena 2i 1401i wiuioiifgiiaiiigiuie f i position- 'of' the cage "25 his" also* determined 95 loo 85 cooperates withthe groove A87 .I Thiefringj i ii'ti springs 89,'90 tend; to force4 theringf84 into for every position of the sleeve 2. The two threads 80, and 22, 23 can, however, only cooperate correctly when their inclinations or pitches are in a determinable ratio to each other. Details tliei'eof and of theoperation of thc described device shall now be explained with reference to Fig. 8.

Assuming the sleeve 2 is so far turned on the shaft l that the point A (Fig. 8) on the sleeve 2 takes up the position A. A point on the cage vsitnated at the point A does not move. however, as fai' as A, but only approximately half as far, i. e.V to A. The associated paths in theV circumferential direction are (l, and Z2 and in the axial direction al and al respectively. rI`he longtiidinal slot 8G in the cage 25 has also been displaced only over the shorter circumferential path (Z2 and the shorter axial path a2. The ball 85- arranged in theslot 86 has, however, moved over the same axial' path al as the sleeve 2 since it engages the annular groove 87 connected to the sleeve 2, while in the circumferential direction it has moved only over the smaller path di, The new position f of the ball 85 is thus only possible ifzthe pitch o of the thread 8() corresponding to the length (Z2 is equal to the axial path al'. The ratio ofthe pitch-of the two threads is n thus determined by. the ratio of the circumferential paths d, and dgythe ball 85 acts as locking` member.V An undesirable adjustment of the cage 25 into one of its extreme positions, determined by the rings 26, 27, is no longer possible with'the described device and aslong as the sleeve 2 is displaced within normal limits, Y 4- The saine eifectmay be attained if instead of the auxiliary thread 80, the annularouide 87 Aand the ball 85 a torsional sirinof :s l s,

100 is provided, as shown in Figui), one end` of the spring being coiiiiected-to the sleeve 2 and the other end to the shaft 1. This spring is so tensioned that it'holds the diierent parts of the `rearingpermanently in Contact with each otherand owing to an initial tensioning it exerts also sucha turning` action that' it causes the required contact between the balls 24 and the thread 22, 23 with a suicient pressure so that the cage 25 is held in the delinite position determinedby the balls 24 when the latter roll without gliding.

I claim: Y

l. In a friction `gear, inV combination, a drivingP shaft, a driven shaft, a rollingtrack provided on a part connected to .the driven shaft, a stationary partliaving a rolling' track, an axially displaceable member operatively connected to the driving shaft and provided with a rolling' track, rolling' inembers en'gafggingV frictionally said rollingtracks, means adapted `to press said rolling members on to said rolling tracks,.whiclimeans in-1 clude a. screw thread interposed betweens'aid adaptedto prevent a deviation of said cage' fromthe position that itassumes by a slilpless rolling movement of said balls.

2. Ina friction gear, in combination, a

driving shaft, a: driven shaft, a rolling track provided on a part connected to the driven shaft, a stationary parthaving a rolling track, anl axially displaceable member oper atively connected tothe driving shaft and provided with a rolling track, rolling members engaging frictionally said rolling tracks, means adapted to press said rolling members on to said rolling tracks, which means include a screw thread interposed between said axially displaceable member and said drivinfr shaft, balls inserted in saidjscrew thread, a 'guide cage for the balls taking part in a helical movement causing the displacement of saiddisplaceable member, and a` torsion spring' operatively connected at its one end to said displaceable member and at its other end to the driving shaft, said spring; having- .JAKoB ARTER.

f axiallydisplaceable member andsaid driv- 

